A prior art microwave switch includes an inductance or high impedance transmission line used as an inductance connected in series between a microwave source and a microwave load; the inductive transmission line has N taps, where N is an integer greater than 1. N shunt diodes are provided, such that one diode is connected to each of the taps. To couple the microwave signal to the load, the diodes are back biased to form capacitive impedances of a low pass filter including the inductane; the filter has a cut off frequency sufficiently high to pass all frequencies in a microwave pass band of interest. To decouple the microwave signal from the load, the diodes are forward biased to provide low impedance paths between the taps of the inductive transmission line and ground.
A problem with this microwave switch is that driver circuitry for the diode requires a significant amount of power to rapidly forward and back bias the diodes. Although it is desirable for the driver to be realized in the same integrated circuit structure as the microwave switch, the driver power dissipation can adversely affect switch utility for many applications.
A microwave switch specification calls for an ON state insertion loss less than 3 db and an OFF state isolation in excess of 48 db over a 0.1-20 gHz frequency range. It is also desirable for such switches to be able to handle a relatively high amount of microwave power, such as 100 milliwatts, and to switch from a fully on to a fully off condition in less than 15 nanoseconds.
It is, accordingly, an object of the present invention to provide a new and improved microwave switch.
Another object of the present invention is to provide a new and improved single pole double throw microwave switch.
A further object of the invention is to provide a microwave switch which, while activated to the on and off states, draws virtually no power from a driver.
A further object of the invention is to provide a new and improved high power, high speed microwave switch having a relatively low on state insertion loss and relatively high off state isolation.
Still another object of the invention is to provide a new and improved microwave structure wherein a switch driver and a switch are realized in a monolithic integrated circuit structure.